Generalized distributed multi-user (MU) transmissions

ABSTRACT

Certain aspects relate to methods and apparatus for wireless communication. The apparatus generally includes a processing system configured to generate a first frame including an indication of unused resources in a first basic service set (BSS) available to be shared with one or more wireless nodes in one or more second BSSs. The apparatus also includes a first interface configured to output the first frame for transmission to the one or more wireless nodes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/052,474, filed Aug. 1, 2018, which claims the benefit of and priorityto U.S. Provisional Patent Application No. 62/541,608, filed Aug. 4,2017, which are assigned to the assignee hereof and hereby expresslyincorporated by reference herein in their entireties.

BACKGROUND I. Field of the Disclosure

The present disclosure relates generally to communication systems, andmore particularly, to methods and apparatus for distributedcommunications using unused resources shared across multiple basicservice sets (BSSs).

II. Description of Related Art

In order to address the issue of increasing bandwidth requirements thatare demanded for wireless communication systems, different schemes arebeing developed to allow multiple user terminals to communicate with asingle access point (AP) or multiple APs by sharing the channelresources while achieving high data throughputs. Multiple Input MultipleOutput (MIMO) technology represents one such approach that has recentlyemerged as a popular technique for the next generation communicationsystems.

A MIMO system employs multiple (NT) transmit antennas and multiple (NR)receive antennas for data transmission. A MIMO channel formed by the NTtransmit and NR receive antennas may be decomposed into NS independentchannels, which are also referred to as spatial channels, whereN_(S)≤min{N_(T), N_(R)}. Each of the NS independent channels correspondsto a dimension. The MIMO system can provide improved performance (suchas higher throughput and greater reliability) if the additionaldimensionalities created by the multiple transmit and receive antennasare utilized.

In wireless networks with multiple APs and multiple user stations(STAs), concurrent transmissions may occur on multiple channels towarddifferent STAs, both in uplink and downlink directions. Many challengesare present in such systems. For example, the AP may transmit signalsusing different standards such as the IEEE 802.11n/a/b/g or the IEEE802.11ac (Very High Throughput (VHT)) standards. A receiver STA may beable to detect a transmission mode of the signal based on informationincluded in a preamble of the transmission packet.

A downlink multi-user MIMO (MU-MIMO) system based on Spatial DivisionMultiple Access (SDMA) transmission can simultaneously serve a pluralityof spatially separated STAs by applying beamforming at the AP's antennaarray. Complex transmit precoding weights can be calculated by the APbased on channel state information (CSI) received from each of thesupported STAs.

In a distributed MU-MIMO system, multiple APs may simultaneously serve aplurality of spatially separated STAs by coordinating beamforming by theantennas of the multiple APs. For example, multiple APs may coordinatetransmissions to each STA.

As the demand for wireless access continues to increase, there exists adesire for further improvements in wireless technology. Preferably,these improvements should be applicable to other multi-accesstechnologies and the communication standards that employ thesetechnologies.

BRIEF SUMMARY

The systems, methods, and devices of the disclosure each have severalaspects, no single one of which is solely responsible for its desirableattributes. Without limiting the scope of this disclosure as expressedby the claims which follow, some features will now be discussed briefly.After considering this discussion, and particularly after reading thesection entitled “Detailed Description” one will understand how thefeatures of this disclosure provide advantages that include improvedcommunications between access points and stations in a wireless network.

Certain aspects of the present disclosure provide an apparatus forwireless communication. The apparatus generally includes a processingsystem configured to generate a first frame including an indication ofunused resources in a first basic service set (BSS) available to beshared with one or more wireless nodes in one or more second BSSs. Theapparatus also includes a first interface configured to output the firstframe for transmission to the one or more wireless nodes.

Certain aspects of the present disclosure provide a method for wirelesscommunications that may be performed, for example, by an apparatus. Themethod generally includes generating a first frame including anindication of unused resources in a first basic service set (BSS)available to be shared with one or more wireless nodes in one or moresecond BSSs. The method also includes outputting the first frame fortransmission to the one or more wireless nodes.

Certain aspects of the present disclosure provide an apparatus forwireless communications. The apparatus generally includes means forgenerating a first frame including an indication of unused resources ina first basic service set (BSS) available to be shared with one or morewireless nodes in one or more second BSSs. The apparatus also includesmeans for outputting the first frame for transmission to the one or morewireless nodes.

Certain aspects of the present disclosure provide a computer-readablemedium having computer executable code stored thereon for wirelesscommunication by an apparatus. The computer executable code includescode for generating a first frame including an indication of unusedresources in a first basic service set (BSS) available to be shared withone or more wireless nodes in one or more second BSSs. The computerexecutable code also includes code for outputting the first frame fortransmission to the one or more wireless nodes.

Certain aspects of the present disclosure provide a wireless node. Thewireless node includes a transmitter and a processing system. Theprocessing system is configured to generate a first frame including anindication of unused resources in a first basic service set (BSS)available to be shared with one or more wireless nodes in one or moresecond BSSs. The transmitter is configured to transmit the first frameto the one or more wireless nodes.

Certain aspects of the present disclosure provide an apparatus forwireless communication. The apparatus generally includes a firstinterface configured to obtain a first frame including an indication ofunused resources in a first basic service set (BSS) available to beshared with the apparatus, wherein the apparatus is in a second BSS. Theapparatus also includes a processing system configured to generate asecond frame including an indication of an intent to use one or more ofthe unused resources. The apparatus further includes a second interfaceconfigured to output the second frame for transmission.

Certain aspects of the present disclosure provide a method for wirelesscommunications that may be performed, for example, by an apparatus. Themethod generally includes obtaining a first frame including anindication of unused resources in a first basic service set (BSS)available to be shared with the apparatus, wherein the apparatus is in asecond BSS. The method also includes generating a second frame includingan indication of an intent to use one or more of the unused resources.The method further includes outputting the second frame fortransmission.

Certain aspects of the present disclosure provide an apparatus forwireless communications. The apparatus generally includes means forobtaining a first frame including an indication of unused resources in afirst basic service set (BSS) available to be shared with the apparatus,wherein the apparatus is in a second BSS. The apparatus also includesmeans for generating a second frame including an indication of an intentto use one or more of the unused resources. The apparatus furtherincludes means for outputting the second frame for transmission.

Certain aspects of the present disclosure provide a computer-readablemedium having computer executable code stored thereon for wirelesscommunication by an apparatus. The computer executable code includescode for obtaining a first frame including an indication of unusedresources in a first basic service set (BSS) available to be shared withthe apparatus, wherein the apparatus is in a second BSS. The computerexecutable code also includes means for generating a second frameincluding an indication of an intent to use one or more of the unusedresources. The computer executable code further includes means foroutputting the second frame for transmission.

Certain aspects of the present disclosure provide a wireless node. Thewireless node includes a receiver, a processing system, and atransmitter. The receiver is configured to receive a first frameincluding an indication of unused resources in a first basic service set(BSS) available to be shared with the wireless node, wherein thewireless node is in a second BSS. The processing system is configured togenerate a second frame including an indication of an intent to use oneor more of the unused resources. The transmitter is configured totransmit the second frame.

To the accomplishment of the foregoing and related ends, the one or moreaspects comprise the features hereinafter fully described andparticularly pointed out in the claims. The following description andthe annexed drawings set forth in detail certain illustrative featuresof the one or more aspects. These features are indicative, however, ofbut a few of the various ways in which the principles of various aspectsmay be employed, and this description is intended to include all suchaspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentdisclosure can be understood in detail, a more particular description,briefly summarized above, may be had by reference to aspects, some ofwhich are illustrated in the appended drawings. It is to be noted,however, that the appended drawings illustrate only certain typicalaspects of this disclosure and are therefore not to be consideredlimiting of its scope, for the description may admit to other equallyeffective aspects.

FIG. 1 is a diagram of an example wireless communications network, inaccordance with certain aspects of the present disclosure.

FIG. 2 is a block diagram of an example access point and examplestations, in accordance with certain aspects of the present disclosure.

FIG. 3 illustrates an example wireless device, in accordance withcertain aspects of the present disclosure.

FIG. 4 illustrates an example of a distributed multi-usermultiple-input-multiple-output (MU-MIMO) system), in accordance withcertain aspects of the present disclosure.

FIG. 5A illustrates a communication system using coordinated downlink(DL) multi-user multiple-input-multiple-output (MU-MIMO), in accordancewith certain aspects of the present disclosure.

FIG. 5B illustrates a communication system using coordinated uplink (UL)multi-user multiple-input-multiple-output (MU-MIMO), in accordance withcertain aspects of the present disclosure.

FIGS. 6A-6C illustrate example communication protocols for coordinatedbeamforming (CoBF) including explicit sounding, in accordance withcertain aspects of the present disclosure.

FIGS. 7A-7C illustrate example communication protocols for CoBFincluding explicit sounding, in accordance with certain aspects of thepresent disclosure.

FIGS. 8A-8B illustrate example communication protocols includingimplicit sounding, in accordance with certain aspects of the presentdisclosure.

FIG. 9 illustrates an example of frequency sharing among multiple basicservice sets, in accordance with certain aspects of the presentdisclosure.

FIG. 10 is a flow diagram of example operations for wirelesscommunication, in accordance with certain aspects of the presentdisclosure.

FIG. 10A illustrates example components capable of performing theoperations shown in FIG. 10 , in accordance with certain aspects of thepresent disclosure.

FIG. 11 is a flow diagram of example operations for wirelesscommunication, in accordance with certain aspects of the presentdisclosure.

FIG. 11A illustrates example components capable of performing theoperations shown in FIG. 11 , in accordance with certain aspects of thepresent disclosure.

FIG. 12 illustrates an example of sharing frequency and spatial streamresources across multiple BSSs for distributed communications, inaccordance with certain aspects of the present disclosure.

FIG. 13 illustrates a group formation protocol for sharing unusedresources for distributed communications, in accordance with certainaspects of the present disclosure.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements disclosed in one aspectmay be beneficially utilized on other aspects without specificrecitation.

DETAILED DESCRIPTION

Various aspects of the disclosure are described more fully hereinafterwith reference to the accompanying drawings. This disclosure may,however, be embodied in many different forms and should not be construedas limited to any specific structure or function presented throughoutthis disclosure. Rather, these aspects are provided so that thisdisclosure will be thorough and complete, and will fully convey thescope of the disclosure to those skilled in the art. Based on theteachings herein one skilled in the art should appreciate that the scopeof the disclosure is intended to cover any aspect of the disclosuredisclosed herein, whether implemented independently of or combined withany other aspect of the disclosure. For example, an apparatus may beimplemented or a method may be practiced using any number of the aspectsset forth herein. In addition, the scope of the disclosure is intendedto cover such an apparatus or method which is practiced using otherstructure, functionality, or structure and functionality in addition toor other than the various aspects of the disclosure set forth herein. Itshould be understood that any aspect of the disclosure disclosed hereinmay be embodied by one or more elements of a claim.

The word “exemplary” is used herein to mean “serving as an example,instance, or illustration.” Any aspect described herein as “exemplary”is not necessarily to be construed as preferred or advantageous overother aspects.

Although particular aspects are described herein, many variations andpermutations of these aspects fall within the scope of the disclosure.Although some benefits and advantages of the preferred aspects arementioned, the scope of the disclosure is not intended to be limited toparticular benefits, uses, or objectives. Rather, aspects of thedisclosure are intended to be broadly applicable to different wirelesstechnologies, system configurations, networks, and transmissionprotocols, some of which are illustrated by way of example in thefigures and in the following description of the preferred aspects. Thedetailed description and drawings are merely illustrative of thedisclosure rather than limiting, the scope of the disclosure beingdefined by the appended claims and equivalents thereof.

The following description is directed to certain implementations for thepurposes of describing the innovative aspects of this disclosure.However, a person having ordinary skill in the art will readilyrecognize that the teachings herein can be applied in a multitude ofdifferent ways. The described implementations may be implemented in anydevice, system or network that is capable of transmitting and receivingRF signals according to any of the IEEE 16.11 standards, or any of theIEEE 802.11 standards, the Bluetooth® standard, code division multipleaccess (CDMA), frequency division multiple access (FDMA), time divisionmultiple access (TDMA), Global System for Mobile communications (GSM),GSM/General Packet Radio Service (GPRS), Enhanced Data GSM Environment(EDGE), Terrestrial Trunked Radio (TETRA), Wideband-CDMA (W-CDMA),Evolution Data Optimized (EV-DO), 1×EV-DO, EV-DO Rev A, EV-DO Rev B,High Speed Packet Access (HSPA), High Speed Downlink Packet Access(HSDPA), High Speed Uplink Packet Access (HSUPA), Evolved High SpeedPacket Access (HSPA+), Long Term Evolution (LTE), AMPS, or other knownsignals that are used to communicate within a wireless, cellular orinternet of things (IOT) network, such as a system utilizing 3G, 4G or5G, or further implementations thereof, technology.

The techniques described herein may be used for various broadbandwireless communication systems, including communication systems that arebased on a single carrier transmission. Aspects may be, for example,advantageous to systems employing Ultra-Wide Band (UWB) signalsincluding millimeter-wave signals. However, this disclosure is notintended to be limited to such systems, as other coded signals maybenefit from similar advantages.

The techniques may be incorporated into (such as implemented within orperformed by) a variety of wired or wireless apparatuses (such asnodes). In some implementations, a node includes a wireless node. Such awireless node may provide, for example, connectivity to or for a network(such as a wide area network (WAN) such as the Internet or a cellularnetwork) via a wired or wireless communication link. In someimplementations, a wireless node may include an access point or a userterminal.

Multiple APs may transmit to multiple receiving user terminals at a timeby using distributed multi-user multiple input multiple output(MU-MIMO). For example, multiple APs may transmit data to a given userterminal at a time, meaning the transmission of data to the userterminal is distributed between the multiple APs. The multiple APs mayutilize beamforming to steer signals spatially to the user terminal. Insome implementations, for the multiple APs to perform distributedMU-MIMO, the multiple APs coordinate the beamforming performed by eachAP to reduce interference for transmitting data to the user terminal. Insome implementations, the multiple APs perform a procedure to form agroup of APs to transmit to the user terminal, as discussed herein. Insome implementations, the multiple APs perform a procedure to form agroup of APs to receive from one or more user terminals, as discussedherein. Further, in some implementations, to coordinate the beamformingbetween the multiple APs, the multiple APs perform a sounding procedureto gather feedback information from the user terminal about wirelesschannels between the multiple APs and the user terminal, as discussedherein. The multiple APs may utilize the feedback information to performbeamforming.

Particular implementations of the subject matter described in thisdisclosure can be implemented to realize one or more of the followingpotential advantages. For example, APs are able to form a group fortransmitting to a user terminal using over the air signaling as opposedto communicating over a backhaul. This may reduce data congestion on thebackhaul. Additionally, the sounding procedures may allow forcoordinated gathering of feedback information by multiple APs from userterminals. Accordingly, the feedback information for the multiple APsmay include channel conditions for each of the multiple APs coordinatedin time, which may improve the accuracy of the beamforming based on thefeedback information. Furthermore, the sounding procedures may limit theamount of data exchanged wirelessly to perform the sounding procedures,which may reduce bandwidth usage of wireless channels.

Example Wireless Communication System

FIG. 1 illustrates a multiple-access Multiple Input Multiple Output(MIMO) system 100 with access points and user terminals. For simplicity,only one access point 110 is shown in FIG. 1 . An access point (AP) isgenerally a fixed station that communicates with the user terminals(UTs) and also may be referred to as a base station or some otherterminology. A user terminal may be fixed or mobile and also may bereferred to as a mobile station, a station (STA), a client, a wirelessdevice, or some other terminology. A user terminal may be a wirelessdevice, such as a cellular phone, a personal digital assistant (PDA), ahandheld device, a wireless modem, a laptop computer, a personalcomputer, etc.

The access point 110 may communicate with one or more user terminals 120at any given moment on the downlink and uplink. The downlink (i.e.,forward link) is the communication link from the access point to theuser terminals, and the uplink (i.e., reverse link) is the communicationlink from the user terminals to the access point. A user terminal alsomay communicate peer-to-peer with another user terminal. A systemcontroller 130 couples to and provides coordination and control for theaccess points.

The MIMO system 100 employs multiple transmit and multiple receiveantennas for data transmission on the downlink and uplink. The accesspoint 110 is equipped with a number N_(ap) of antennas and representsthe multiple-input (MI) for downlink transmissions and themultiple-output (MO) for uplink transmissions. A set N_(u) of selecteduser terminals 120 collectively represents the multiple-output fordownlink transmissions and the multiple-input for uplink transmissions.In some implementations, it may be desirable to have N_(ap)≥N_(u)≥1 ifthe data symbol streams for the N_(u) user terminals are not multiplexedin code, frequency or time by some means. N_(u) may be greater thanN_(ap) if the data symbol streams can be multiplexed using differentcode channels with CDMA, disjoint sets of sub-bands with OFDM, and soon. Each selected user terminal transmits user-specific data to andreceives user-specific data from the access point. In general, eachselected user terminal may be equipped with one or multiple antennas(i.e., N_(ut)≥1). The N_(u) selected user terminals can have the same ordifferent number of antennas.

The MIMO system 100 may be a time division duplex (TDD) system or afrequency division duplex (FDD) system. For a TDD system, the downlinkand uplink share the same frequency band. For an FDD system, thedownlink and uplink use different frequency bands. The MIMO system 100also may utilize a single carrier or multiple carriers for transmission.Each user terminal may be equipped with a single antenna (such as inorder to keep costs down) or multiple antennas (such as where theadditional cost can be supported). The MIMO system 100 may represent ahigh speed Wireless Local Area Network (WLAN) operating in a 60 GHzband.

FIG. 2 illustrates example components of the access point 110 andstation 120 illustrated in FIG. 1 , which may be used to implementaspects of the present disclosure. One or more components of the accesspoint 110 and station 120 may be used to practice aspects of the presentdisclosure. For example, antenna 224, transmitter/receiver unit 222,processors 210, 220, 240, 242, and/or controller 230 or antenna 252,transmitter/receiver 254, processors 260, 270, 288, and 290, and/orcontroller 280 may be used to perform the operations described hereinand illustrated with reference to FIGS. 10, 10A, 11 and 11A.

FIG. 2 shows a block diagram of the access point/base station 110 andtwo user terminals/user equipments 120 m and 120 x in a MIMO system 100.The access point 110 is equipped with N_(ap) antennas 224 a through 224ap. The user terminal 120 m is equipped with N_(ut,m) antennas 252 mathrough 252 mu, and the user terminal 120 x is equipped with N_(ut,x)antennas 252 xa through 252 xu. The access point 110 is a transmittingentity for the downlink and a receiving entity for the uplink. Each userterminal 120 is a transmitting entity for the uplink and a receivingentity for the downlink. As used herein, a “transmitting entity” is anindependently operated apparatus or device capable of transmitting datavia a frequency channel, and a “receiving entity” is an independentlyoperated apparatus or device capable of receiving data via a frequencychannel. In the following description, the subscript “dn” denotes thedownlink, the subscript “up” denotes the uplink, N_(up) user terminalsare selected for simultaneous transmission on the uplink, and N_(dn)user terminals are selected for simultaneous transmission on thedownlink. Moreover, N_(up) may or may not be equal to N_(dn), andN_(up), and N_(dn) may include static values or can change for eachscheduling interval. Beamforming (such as beam-steering) or some otherspatial processing techniques may be used at the access point and userterminal.

On the uplink, at each user terminal 120 selected for uplinktransmission, a TX data processor 288 receive traffic data from a datasource 286 and control data from a controller 280. The controller 280may be coupled with a memory 282. The TX data processor 288 processes(such as encodes, interleaves, and modulates) the traffic data{d_(up,m)} for the user terminal based on the coding and modulationschemes associated with the rate selected for the user terminal andprovides a data symbol stream {s_(up,m)}. A TX spatial processor 290performs spatial processing on the data symbol stream {s_(up,m)} andprovides N_(ut,m) transmit symbol streams for the N_(ut,m) antennas.Each transmitter unit (TMTR) 254 receives and processes (such asconverts to analog, amplifies, filters, and frequency upconverts) arespective transmit symbol stream to generate an uplink signal. TheN_(ut,m) transmitter units 254 provide N_(ut,m) uplink signals fortransmission from the N_(ut,m) antennas 252 to the access point 110.

A number N_(up) of user terminals may be scheduled for simultaneoustransmission on the uplink. Each of these user terminals performsspatial processing on its data symbol stream and transmits its set oftransmit symbol streams on the uplink to the access point.

At the access point 110, the N_(ap) antennas 224 a through 224 apreceive the uplink signals from all N_(up) user terminals transmittingon the uplink. Each antenna 224 provides a received signal to arespective receiver unit (RCVR) 222. Each receiver unit 222 performsprocessing complementary to that performed by the transmitter unit 254and provides a received symbol stream. An RX spatial processor 240performs receiver spatial processing on the N_(ap) received symbolstreams from the N_(ap) receiver units 222 and provides N_(up) recovereduplink data symbol streams. The receiver spatial processing is performedin accordance with the channel correlation matrix inversion (CCMI),minimum mean square error (MMSE), successive interference cancellation(SIC), or some other technique. Each recovered uplink data symbol stream{s_(up,m)} is an estimate of a data symbol stream {s_(up,m)} transmittedby a respective user terminal. An RX data processor 242 processes (suchas demodulates, de-interleaves, and decodes) each recovered uplink datasymbol stream {s_(up,m)} in accordance with the rate used for thatstream to obtain decoded data. The decoded data for each user terminalmay be provided to a data sink 244 for storage and a controller 230 forfurther processing.

On the downlink, at the access point 110, a TX data processor 210receives traffic data from a data source 208 for N_(dn) user terminalsscheduled for downlink transmission, control data from a controller 230,and possibly other data from a scheduler 234. The various types of datamay be sent on different transport channels. The TX data processor 210processes (such as encodes, interleaves, and modulates) the traffic datafor each user terminal based on the rate selected for that userterminal. The TX data processor 210 provides Nan downlink data symbolstreams for the Nan user terminals. A TX spatial processor 220 performsspatial processing on the Nan downlink data symbol streams, and providesN_(ap) transmit symbol streams for the N_(ap) antennas. Each transmitterunit (TMTR) 222 receives and processes a respective transmit symbolstream to generate a downlink signal. The N_(ap) transmitter units 222provide N_(ap) downlink signals for transmission from the N_(ap)antennas 224 to the user terminals. The decoded data for each STA may beprovided to a data sink 272 for storage and/or a controller 280 forfurther processing.

At each user terminal 120, the N_(ut,m) antennas 252 receive the N_(ap)downlink signals from the access point 110. Each receiver unit (RCVR)254 processes a received signal from an associated antenna 252 andprovides a received symbol stream. An RX spatial processor 260 performsreceiver spatial processing on N_(ut,m) received symbol streams from theN_(ut,m) receiver units 254 and provides a recovered downlink datasymbol stream {s_(dn,m)} for the user terminal. The receiver spatialprocessing can be performed in accordance with the CCMI, MMSE, or otherknown techniques. An RX data processor 270 processes (such asdemodulates, de-interleaves, and decodes) the recovered downlink datasymbol stream to obtain decoded data for the user terminal.

At each user terminal 120, the N_(ut,m) antennas 252 receive the N_(ap)downlink signals from the access point 110. Each receiver unit (RCVR)254 processes a received signal from an associated antenna 252 andprovides a received symbol stream. An RX spatial processor 260 performsreceiver spatial processing on N_(ut,m) received symbol streams from theN_(ut,m) receiver units 254 and provides a recovered downlink datasymbol stream {s_(dn,m)} for the user terminal. The receiver spatialprocessing is performed in accordance with the CCMI, MMSE, or some othertechnique. An RX data processor 270 processes (such as demodulates,de-interleaves, and decodes) the recovered downlink data symbol streamto obtain decoded data for the user terminal.

FIG. 3 illustrates various components that may be utilized in a wirelessdevice 302 that may be employed within the MIMO system 100. The wirelessdevice 302 is an example of a device that may be configured to implementthe various methods described herein. The wireless device 302 may be anaccess point 110 or a user terminal 120.

The wireless device 302 may include a processor 304 which controlsoperation of the wireless device 302. The processor 304 also may bereferred to as a central processing unit (CPU). Memory 306, which mayinclude both read-only memory (ROM) and random access memory (RAM),provides instructions and data to the processor 304. A portion of thememory 306 also may include non-volatile random access memory (NVRAM).The processor 304 typically performs logical and arithmetic operationsbased on program instructions stored within the memory 306. Theinstructions in the memory 306 may be executable to implement themethods described herein.

The wireless device 302 also may include a housing 308 that may includea transmitter 310 and a receiver 312 to allow transmission and receptionof data between the wireless device 302 and a remote location. Thetransmitter 310 and the receiver 312 may be combined into a transceiver314. A plurality of transmit antennas 316 may be attached to the housing308 and electrically coupled to the transceiver 314. The wireless device302 also may include (not shown) multiple transmitters, multiplereceivers, and multiple transceivers.

The wireless device 302 also may include a signal detector 318 that maybe used in an effort to detect and quantify the level of signalsreceived by the transceiver 314. The signal detector 318 may detect suchsignals as total energy, energy per subcarrier per symbol, powerspectral density and other signals. The wireless device 302 also mayinclude a digital signal processor (DSP) 320 for use in processingsignals.

The various components of the wireless device 302 may be coupledtogether by a bus system 322, which may include a power bus, a controlsignal bus, and a status signal bus in addition to a data bus.

Example Distributed MU-MIMO

As discussed with respect to FIGS. 1-3 , a single AP 110 may transmit tomultiple receiving user terminals 120 at a time by using multi-user (MU)MIMO (MU-MIMO). In particular, the AP 110 includes multiple antennas224. Using the multiple antennas 224, the AP 110 can utilize beamformingto focus the energy of a transmitted signal spatially (such as to aparticular user terminal 120 as a spatial stream). In order to performbeamforming, the AP 110 may exchange frames with the user terminal 120to measure a channel between the AP 110 and the user terminal 120. Forexample, the AP 110 may transmit a null data packet (NDP) including oneor more long training fields (LTFs) that the user terminal 120 uses tomeasure the channel. The user terminal 120 may generate a channelfeedback information (such as a feedback matrix) based on the channelmeasurements, and send the feedback matrix to the AP 110. Using thefeedback matrix, the AP 110 may derive a steering matrix, which is usedto determine how to transmit a signal on each antenna 224 of the AP 110to perform beamforming. For example, the steering matrix may beindicative of a phase shift, power level, etc. to transmit a signal oneach of the antennas 224. For example, the AP 110 may be configured toperform similar beamforming techniques as described in the 802.11acstandard.

In some implementations, multiple APs 110 may be configured to transmitto one or more receiving user terminals 120 at a time utilizingdistributed MU-MIMO. There may be multiple different types of MU-MIMOtransmissions, including coordinated beamforming (CoBF) and jointprocessing transmission (JT).

FIG. 4 illustrates a distributed MU-MIMO system 400. As shown, system400 includes an AP 110 a and an AP 110 b. The APs 110 a and 110 b, insome implementations, refer back to the AP 110 described with respect toFIG. 1 . The AP 110 a is shown as part of a first basic service set(BSS), BSS1, and the AP 110 b is shown as part of a second BSS, BSS2.The AP 110 a and the AP 110 b may be neighboring APs. Further, portionsof the coverage area of the AP 110 a may overlap with portions of thecoverage area of BSS2, leading to an overlapping BSS (OBSS) situation.Communications by the AP 110 a with user terminals in BSS1 may bereferred to as in BSS communications. Similarly, communication by the AP110 b with user terminals in BSS2 may be referred to as in BSScommunications. Further, communications by the AP 110 a with userterminals in BSS2 may be referred to as OBSS communications, andcommunications by the AP 110 b with user terminals in BSS1 may bereferred to as OBSS communications.

In CoBF, signals (such as data) for a given user terminal may betransmitted by only a single AP. For example, the user terminals 120 aand 120 b are shown as part of BSS1 and therefore only the AP 110 a maytransmit signals intended for the user terminals 120 a and 120 b.Further, user terminals 120 c and 120 d are shown as part of BSS2 andtherefore only the AP 110 b may transmit signals intended for the userterminals 120 c and 120 d. The user terminals 120 a through 120 d, insome implementations, refer back to the user terminal 120 described withrespect to FIG. 1 . However, as discussed the coverage area of the AP110 a and the AP 110 b may overlap, and therefore signals transmitted bythe AP 110 a may reach the user terminals 120 c and 120 d in BSS2 asOBSS signals. Similarly, signals transmitted by the AP 110 b may reachthe user terminals 120 a and 120 d in BSS1 as OBSS signals. In CoBF, theAPs 110 a and 110 b may be configured to perform beamforming to formnulls in the direction of user terminals in OBSS, such that any signalsreceived at an OBSS user terminal are of a low power. For example, theAP 110 a may be configured to perform beamforming to form nulls towardthe user terminals 120 c and 120 d, and the AP 110 b may be configuredto form nulls toward the user terminals 120 a and 120 b to limit theinterference at the user terminals. Accordingly, in CoBF, APs areconfigured to form nulls for OBSS user terminals and configured tobeamform signals to in-BSS user terminals.

In JT, signals for a given user terminal may be transmitted by multipleAPs. For example, one or more of user terminals 120 a through 120 d mayreceive signals from both the AP 110 a and the AP 110 b. For themultiple APs to transmit data to a user terminal, the multiple APs mayall need a copy of the data to be transmitted to the user terminal.Accordingly, the APs may need to exchange the data (such as through abackhaul) between each other for transmission to a user terminal. Forexample, the AP 110 a may have data to transmit to user terminal 120 a,and may further communicate that data over a backhaul to the AP 110 b.The AP 110 a and the AP 110 b may then beamform signals including thedata to the user terminal 120 a.

In some implementations, in JT, the antennas of the multiple APstransmitting to one or more user terminals may be considered as onelarge antenna array (such as virtual antenna array) used for beamformingand transmitting signals. Accordingly, similar beamforming techniques asdiscussed and used for transmitting from multiple antennas of a singleAP to one or more user terminals, may instead be used for transmittingfrom multiple antennas of multiple APs. For example, the samebeamforming, calculating of steering matrices, etc. for transmittingfrom multiple antennas of the AP 110 a, may be applied to transmittingfrom the multiple antennas of both the AP 110 a and the AP 110 b. Themultiple antennas of the multiple APs may be able to form signals on aplurality of spatial streams (such as limited by the number ofantennas). Accordingly, each user terminal may receive signals on one ormore of the plurality of spatial streams. In some implementations, eachAP may be allocated a certain number of the plurality of spatial streamsfor transmission to user terminals in the BSS of the AP. Each spatialstream may be identified by a spatial stream index.

In some implementations, various factors may affect distributed MU-MIMO.For example, one factor may be channel feedback accuracy. As discussed,to perform beamforming APs may exchange signals with user terminals overa communication channel, and the user terminals may make measurements ofthe channel based on the exchanged signals. The user terminals mayfurther send information regarding the channel measurements to the APsas channel feedback information. The APs may utilize the channelfeedback information to perform beamforming. However, the channelconditions may change between when the APs receive the channel feedbackinformation and when the APs actually transmit signals on the channel.This may be referred to as channel aging. Further, there may beinaccuracy due to quantization of the information included in thechannel feedback information. This may impact both CoBF and JTdistributed MU-MIMO and lead to leakage and interference.

Another factor may be phase offsets between APs. For example, APs maytransmit with different phases due to timing synchronization differencesbetween the APs. Further, the difference in phases may drift or change(such as due to phase noise, timing drift, carrier frequency offset(CFO) drift, etc.) between when the channel feedback information isreceived and when the APs transmit to the user terminals. This change inphase difference may not affect CoBF significantly as each AP performsbeamforming independently. However, this change in phase difference mayaffect JT as the APs perform beamforming together.

Another factor may be timing offset. For example, the delay spread,filter delay, and arrival time spread of APs using JT and CoBF may needto be absorbed with a cyclic prefix (CP). For JT, additionally, therelative timing offset across APs (e.g., the change in timing offsetbetween when the channel feedback information is measured and when thesignals are transmitted) also may affect phase offsets and may need tobe further controlled.

Another factor may be CFO. In CoBF, the synchronization requirements forCFO may be reduced as compared to JT. Another factor may be gainmismatch, where different APs use different gain states while measuringchannels of user terminals. This may have a larger effect on JT thanCoBF. In some implementations of CoBF, the largest gain may beapproximately 75% of the minimum of number of transmit antennas of anyof the APs. In some implementations of JT, the largest gain may beapproximately 75% of the sum of the transmit antennas of all the APs.

In some implementations, in MU-MIMO for a single AP transmitting tomultiple user terminals, to perform channel measurements forbeamforming, all the transmit antennas of the AP are sounded together,meaning that all the transmit antennas transmit NDP during the sametransmission time interval (such as TTI, frame, subframe, etc.). Allantennas may be sounded together, because if NDPs for each antenna weretransmitted at different TTIs, they may be transmitted with differentphases and the receiver automatic gain control (RxAGC) at each userterminal receiving the NDPs may be different for different TTIs, whichmay make it difficult to stitch together measurements from the differentNDPs. Further, the relative timing among all transmit antennas fortransmitting NDP at the same TTI is constant for all the transmitantennas, and remains the same for when the NDP is transmitted and forwhen data is later transmitted to the user terminals based on channelfeedback information. Therefore, there is no change in relative timingbetween NDP transmission and data transmission, thereby ensuring betterbeamforming.

In some implementations, all antennas for multiple APs may be soundedtogether to transmit NDP together at the same TTI for JT in a jointsounding procedure, to avoid issues discussed. In some implementations,the NDPs of different APs may be sounding at the same TTI using one ormore techniques such as time-division multiplexing (TDM), code-divisionmultiplexing (CDM) (such as using a P-matrix), and frequency-divisionmultiplexing (FDM).

For CoBF, the beamforming direction of one AP does not depend on thechannels between user terminals and other APs. Accordingly, only loosesynchronization may be needed between APs. Therefore, for CoBF, inaddition to being able to use a joint sounding procedure, a sequentialsounding procedure can be used where APs sound one at a time in separateTTIs and transmit NDPs at different TTIs per AP.

Example Coordinated Downlink (DL) and Uplink (UL) Communications

In downlink (DL) MU-MIMO, multiple stations may belong to one basicservice set (BSS) transmitting in the DL. Other BSSs (e.g., OBSSs)within “hearing” range may defer (not transmit on the medium) inresponse to detecting an on-going transmission. Different BSSs inhearing range of each other may use time-divisional multiplexing (TDM)to transmit in the DL. In coordinated DL MU-MIMO, multiple BSSs carryout simultaneous DL transmissions. Un-used receive spatial dimensions atthe AP may be used to null the interference from the other BSStransmissions. This enables a greater degree of spatial multiplexingwhen there are un-used spatial dimension within the BSS. In other words,the un-used spatial dimensions may allow for concurrent OBSStransmissions in DL.

FIG. 5A illustrates a communication system using coordinated DL MU-MIMO,in accordance with certain aspects of the present disclosure. Asillustrated, the signal from each AP is transmitted to only stationswithin their respective BSSs, as shown by the solid lines representingdata transmissions from the AP the STAs that are associated with the AP.The data transmissions from the APs cause interference to the other OBSSstations, as illustrated by the dotted lines. Un-used dimensions at theAP may be used to get rid of (e.g., null out) interference from OBSSAPs.

In uplink (UL) MU-MIMO, multiple stations may belong to one basicservice set (BSS) transmitting in the UL. Other BSSs within hearingrange may defer to an on-going transmission. Different BSSs in hearingrange of each other may use time-divisional multiplexing (TDM) totransmit in the UL. In coordinated UL MU-MIMO, multiple BSSs may carryout simultaneous UL transmissions. As with DL MU-MIMO, un-used receivespatial dimensions at an AP may be used to null the interference fromthe other BSS (OBSS) transmissions, enabling a greater degree of spatialmultiplexing and allowing for concurrent OBSS transmissions.

FIG. 5B illustrates a communication system using coordinated UL MU-MIMO,in accordance with certain aspects of the present disclosure. Asillustrated, the signal from each station is transmitted to only one APwithin their respective BSSs, as shown by the solid lines representingdata transmissions to the AP the STAs are associated with. The datatransmissions from the STAs cause interference to the other OBSS APs, asillustrated by the dotted lines. Un-used dimensions at each AP may beused to get rid of (e.g., null out) interference from OBSS STAs.

Example Sounding Procedures for Distributed Communications

In some cases, distributed communications (e.g., DL or UL distributed MUtransmissions) may include one or more synchronization protocols. Usingcoordinated beamforming (CoBF) as a reference example of a type ofdistributed communications, a variety of sounding options can be used tosynchronize APs and/or UTs in multiple BSSs for distributedcommunications. As illustrative but non-limiting examples, two highlevel sounding options for explicit sounding with each high levelsounding option including three sub-options are described herein.

As will be described in greater detail below, the high level soundingoptions may include sequential sounding (communication protocols600A-600C in FIGS. 6A-6C) and joint sounding (communication protocols700A-700C in FIGS. 7A-7C). Sequential sounding may involve one null datapacket (NDP) transmission per AP and may sound one AP at a time. Inthese cases, existing sounding sequences (e.g., 802.11ax soundingsequence(s)) may be leveraged with certain modifications. As an examplemodification, a null data packet announcement (NDPA) may address OBSSSTAs. Joint sounding may use one NDP to sound Tx chains of all the APs.Joint sounding may use slightly less overhead due to certain preamblesavings. The NDP may be time division multiplexed (TDM'd), code divisionmultiplexed (CDM'd) (P matrix), or frequency division multiplexed(FDM'd) among Tx chains of all APs.

With respect to the sequential sounding options, FIG. 6A shows anexample communication protocol 600A for CoBF utilizing explicitsounding. In particular, communication protocol 600A includes sequentialNDP transmissions, such that a single AP at a time transmits an NDPA andNDP. The NDPA transmission may identify all STAs and number of streamsbeing allocated to each STA. Further, the NDPA may serve the purpose ofannouncing the NDP transmission and may serve as a synchronizationmessage as well. In one or more cases, as shown, an optional triggerframe may be provided after the NDPA and NDP transmissions. In somecases, the trigger frame indicates when the different stations shouldsend the solicited (CSI) feedback. The stations (STA1 through STA4) maythen respond by transmitting feedback using UL MU-MIMO to thecorresponding AP that sent the NDPA and NDP. Using the CSI providedduring this feedback portion of the protocol, distributed transmissions(Distr MU Tx) may follow along with acknowledgements (ACK) from thestations (STA1 through STA4) as shown. The acknowledgements may be sentusing UL MU (can be OFDMA). In one or more cases the ACKs of the twoBSSs may be sent in parallel using coordinated UL MU-MIMO.

FIG. 6B shows another example communication protocol 600B for CoBFincluding explicit sounding. In particular, communication protocol 600Bshows sequential NDP transmissions along with UL MU-MIMO where both APsreceive all four feedback streams without nulling. Compared tocommunication protocol 600A in FIG. 6A, the master AP and the slave APmay transmit their respective NDPA and NDP sequentially. This may befollowed by an optional trigger frame. The stations (STA1, STA2, STA3,and STA4) may each then transmit feedback using UL MU-MIMO that containsinformation for channels to both the master AP and the slave AP.Compared to communication protocol 600A in FIG. 6A, this may be doneusing a single protocol data unit (PDU), such as a physical PDU (PPDU),as shown in the figure.

Rate and power control may be complex with the communication protocols600A and 600B as illustrated in FIGS. 6A and 6B, respectively.Therefore, other variations on these protocols may be provided inaccordance with certain aspects. As an example, in protocols 600A and600B, the UL MU-MIMO feedback may consist of STAs 1, 2, 3 and 4transmitting their CSI to the AP together. An AP may receive UL MU-MIMOwith STAs of its own BSS and STAs of an OBSS. However, the powers ofin-BSS and OBSS STAs might be very different, making rate and powercontrol more complex.

FIG. 6C shows another communication protocol 600C for providing CSIfeedback (e.g., for explicit sounding) that may help avoid or reducecomplexity that may be associated with communication protocols 600A and600B. Particularly, the communication protocol 600C includes sequentialNDP and coordinated UL MU-MIMO where multiple APs receive CSI feedbacktogether while using spatial dimensions to null out some streams. Asshown, a master AP may transmit an NDPA, an NDP, and an optional triggerframe followed by a slave AP transmitting its own NDPA and NDP. Comparedto communication protocols 600A and 600B in FIGS. 6A and 6B,respectively, the stations STA1 and STA2 (associated with the master AP)in communication protocol 600C in response to the NDPA and NDPtransmissions may, at a first time, transmit feedback using UL MU-MIMOto the master AP that contains channels to the master AP only. In theillustrated example, at the same first time, feedback from stations STA3and STA4 (associated with the slave AP) was also sent to the slave APthat contains channels to slave AP only.

At a second time, the stations STA1-STA4 switch and STA1 and STA2transmit to the slave AP, while STA3 and STA4 transmit to the master AP,as shown, using separate PPDUs. An optional trigger frame may betransmitted between the first and second time by the master AP as shown.What follows then may include distributed transmissions (Distr MU Tx)and acknowledgements (ACK) from the stations (STA1 through STA4). Theacknowledgments may be sent using UL MU (e.g., OFDMA). In one or morecases, the ACKs of the two BSSs may be sent in parallel usingcoordinated UL MU-MIMO.

Various options may be provided for the communication protocols600A-600C. For example, for the communication protocol 600A, one BSS ata time may provide a collection of CSI feedbacks from all STAs. For thecommunication protocol 600B, all STAs may transmit CSI together in acombined packet that contains CSI to all APs. For the communicationprotocol 600C, STAs may transmit their own APs first and subsequently toOBSS APs. In one or more cases, dual triggers (one from each AP) beforea set of UL feedbacks may be implemented. Further, exact location (intime) of triggers may vary from the ones shown in FIGS. 6A-6C.

With respect to the joint sounding options, FIG. 7A illustrates acommunication protocol 700A for CoBF including explicit sounding. Inparticular, communication protocol 700A may include joint NDPtransmission (e.g., NDP transmitted jointly from both APs), regular ULMU-MIMO, and separate feedback packets. For example, all the APs may besounded with one NDP. The master AP may then receive feedback from allstations (STA1-STA4) using UL MU-MIMO at a first time that containschannels to the master AP only. The slave AP may then receive feedbackfrom stations (STA1-STA4) using UL MU-MIMO at a second time thatcontains channels to the slave AP only. What follows then may includedistributed transmissions (Distr MU Tx) and acknowledgements (ACK) fromthe stations (STA1 through STA4). The acknowledgements may be sent usingUL MU (e.g., OFDMA). In one or more cases, the ACKs of the two BSSs maybe sent in parallel using coordinated UL MU-MIMO.

FIG. 7B illustrates another example communication protocol 700B (e.g.,explicit sounding) for CoBF that includes joint NDP transmission,regular UL MU-MIMO, and combined feedback packets. For example, all theAPs may be sounded with one NDP. Compared to communication protocol 700Ain FIG. 7A, the master AP and slave AP in response to the joint NDPtransmission may then both receive feedback from stations STA1-STA4using UL MU-MIMO at a first time that contains channels to both masterand slave APs using a single PPDU.

FIG. 7C illustrates another example communication protocol 700C for CoBF(e.g., with explicit sounding) that includes joint NDP transmission,coordinated UL MU-MIMO, and separate feedback packets. For example, allthe APs may be sounded with one NDP. Compared to communication protocols700A and 700B in FIGS. 7A and 7B, respectively, the master AP may thenreceive feedback from stations STA1 and STA2 using UL MU-MIMO at a firsttime that contains channels to master AP only. The slave AP may receivefeedback from stations STA3 and STA4 using UL MU-MIMO at the same firsttime that contains channels to the slave AP only. At a second(subsequent) time, the master AP may receive feedback from STA3 andSTA4, while the slave AP receives feedback from STA1 and STA2, as shown.

Various options may be provided for the communication protocols700A-700C. For example, for the communication protocol 700A, one BSS ata time may provide collection of CSI feedbacks from all STAs along witha joint NDP. For the communication protocol 700B, all STAs may transmitCSI together in a combined packet that contains CSI to all APs alongwith a joint NDP. For the communication protocol 700C, STAs may transmitto their own APs first and then they may transmit to their OBSS APsalong with joint NDP. In one or more cases, dual triggers (one from eachAP) before a set of UL feedbacks may be implemented. Further, exactlocation (in time) of triggers may vary from the ones shown in FIGS.7A-7C.

In some cases, additional sounding options may include one or moreimplicit sounding options. For example, an implicit sounding option mayinclude separate UL NDP transmission per STA (e.g., communicationprotocol 800A in FIG. 8A) and/or joint UL NDP transmission from all STAs(e.g., communication protocol 800B in FIG. 8B).

FIG. 8A illustrates a communication protocol 800A including implicitsounding that includes separate NDP transmission for each station. Forexample, as illustrated, one station at a time (e.g., STA1, then STA2,then STA3, then STA4) transmits UL NDP transmissions. The DL channelestimation (used for subsequent distributed DL transmissions) may relyon the UL NDP from the STAs. These UL NDP transmissions may then befollowed by the optional trigger for CFO/Timing synchronization that mayallow for group or stream allocation adjustments. What follows then mayinclude distributed transmissions (Distr MU Tx) and acknowledgements(ACK) from the stations (STA1 through STA4). The acknowledgements may besent using UL MU (e.g., OFDMA). In one or more cases, the ACKs of thetwo BSSs may be sent in parallel using coordinated UL MU-MIMO.

FIG. 8B illustrates another example communication protocol 800Bincluding implicit sounding. Compared to communication protocol 800A inFIG. 8A, the communication protocol 800B includes joint NDP for allstations such that all stations (STA1-STA4) transmit the UL NDPtransmissions at one time. In this example, the DL channel estimationmay therefore rely ono the UL NDPs simultaneously sent from all of theSTAs.

In one or more cases, when the NDPs are being sent together incommunication protocol 800B, the LTFs may be multiplexed using any ofthe techniques described above with reference to DL NDPs transmittedfrom multiple APs (e.g., FDM, P-matrix, and/or TDM). In one or morecases, ACKs may be sent in one BSS using UL MU-MIMO and sequentiallyacross BSSs. In some cases, ACKs may be sent using OFDMA as well.Further, in some cases, the ACKs of multiple BSSs may be sent togetheras well, for example, using coordinated UL MU-MIMO, coordinated ULOFDMA, or a mixture thereof.

Note that, for the communication protocols 600A-600C in FIGS. 6A-6C, thecommunication protocols 700A-700C in FIGS. 7A-7C, and the communicationprotocols 800A-800B in FIGS. 8A-8B, it may be assumed that groupformation has taken place before the NDPA transmission(s) shown in eachcommunication protocol. Assuming the group formation has taken place,the NDPA transmission(s) may identify all STAs and number of streamsbeing allocated to each STA.

Further, there may be various options to multiplex NDPs from differentAPs or STAs transmitted at the same time. For example, using frequencydivision multiplexing, each stream may be allocated different tones ineach LTF symbol. In some cases, along with FDM, beam steering matrix(P-matrix) may be used to multiplex the streams of an AP, whiledifferent APs are allocated non-overlapping tones. As an alternative,all streams (from all APs) could be multiplexed using a large P-matrix.Using time division multiplexing, one stream may be allocated one LTF.This TDM approach could be combined with P-matrix multiplexing, forexample, with one AP's streams multiplexed using P-matrix, whiledifferent APs are active on different LTF symbols.

Example of Generalized Distributed MU Transmissions

Aspects presented herein provide group formation protocols fordistributed (DL or UL) communications (e.g., across multiple BSSs).

In certain systems (e.g., 802.11ax), an AP in one BSS may transmit to orreceive from multiple STAs (e.g., in the same BSS) simultaneously whilegiving the STAs orthogonal frequency or spatial stream resources. Forexample, simultaneous transmission can be achieved using DL OFDMA (whichmay be combined with MU-MIMO). Similarly, simultaneous reception can beachieved using UL OFDMA (which may be combined with MU-MIMO).Simultaneous reception using UL OFDMA may be referred to as UL MUtransmission, which may be trigger based.

However, while some systems may support simultaneous transmissions andreceptions to and from STAs within a BSS, such systems may not supportmultiple BSSs (e.g., within hearing range of each other) using unusedresources within one or more of the multiple BSSs for simultaneoustransmissions/receptions. The unused resources, for example, may includeunused frequency resources within a BSS, unused spatial stream resourcesat an apparatus (e.g., AP) within a BSS, etc.

FIG. 9 illustrates an example of two neighboring BSSs sharing frequencyresources for distributed communications (e.g., coordinated OFDMA), inaccordance with aspects of the present disclosure. In this example, STAs1, 2, and 3 belong to a first BSS (BSS1) and STAs 4, 5, and 6 belong toa second BSS (BSS2). BSS1 may use 10 MHz portion 902 of the 40 MHzspectrum for communications with STAs 1, 2, and 3 in BSS 1. BSS2 may useanother 10 MHz portion 904 of the 40 MHz spectrum for communicationswith STAs 4 and 5 in BSS2 and a 20 MHz portion 906 of the 40 MHzspectrum for communications with STA 6 in BSS2.

APs in each of BSS1 and BSS2 may simultaneously transmit/receive to andfrom their respective STAs on the respective frequency resources. Forexample, APs in BSS1 may transmit to STAs 1, 2, and 3 at a same timethat APs in BSS2 transmit to STAs 4, 5, and 6. APs in BSS1 and BSS2 mayuse multi-AP DL OFDMA, which generally involves transmissions frommultiple APs starting at the same time, to transmit to their STAs.Similarly, STAs 1, 2, and 3 may transmit to APs in BSS1 at a same timethat STAs 4, 5, and 6 transmit to APs in BSS2. STAs may use UL OFDMA,which generally involves transmissions from STAs starting at the sametime, to transmit to APs.

In this example, STAs 1, 2, and 3 may be multiplexed (e.g., in thespatial domain) using MU-MIMO, and STAs 4-5 may be multiplexed (e.g., inthe spatial domain) using MU-MIMO. Further, note that the amount offrequency resources, number of STAs and BSSs in FIG. 9 are providedmerely as reference examples, and that any amount of frequency resourcesmay be shared with any number of STAs and BSSs.

Referring back to FIG. 5A, FIG. 5A illustrates an example of sharingspatial stream resources across multiple BSSs (e.g., in the case whereDL coordinated beamforming is used for DL distributed MU-MIMO). In thisexample, two APs (AP1 and AP2) may transmit simultaneously to theirrespective STAs. As shown, AP1 may use its extra spatial dimensions(represented by dashed lines) to form nulls to the receivers oftransmissions in BSS2, e.g., to limit the interference (due totransmissions from AP1) at the receivers in BSS2. Likewise, AP2 may useits extra spatial dimensions (represented by dashed lines) to form nullsto the receivers of transmissions in BSS1, e.g., to limit theinterference (due to transmission from AP2) at the receivers in BSS1.FIG. 5B shows a similar example of sharing spatial stream resourcesacross multiple BSSs for UL distributed MU-MIMO.

Aspects presented herein provide techniques and apparatus for enabling a(first) BSS sharing frequency/spatial stream resources with at leastanother (second) BSS to simultaneously transmit/receive with one or moreunused frequency/spatial stream resources in the other BSS. Note thatwhile certain aspects of the present disclosure describe operationsperformed by a master AP (that is part of a BSS), operations describedherein may be performed by another entity that may not be part of a BSS,such as a device acting as a central processing unit, scheduler, orcoordinator.

FIG. 10 a flow diagram of example operations 1000 for wirelesscommunications by an apparatus, in accordance with aspects of thepresent disclosure. The operations may be performed by an apparatus suchas a master access point (e.g., AP 110) or other entity, such as acentral processing unit, scheduler, or coordinator.

Operations 1000 begin, at 1002, where the apparatus generates a firstframe including an indication of unused resources in a first basicservice set (BSS) available to be shared with one or more wireless nodes(e.g., APs/STAs) in one or more second BSSs. The unused resources mayinclude at least one of unused spatial dimensions available at theapparatus (e.g., assuming the apparatus is in the first BSS), unusedspatial dimensions available at another apparatus in the first BSS, orunused portions of spectrum in the first BSS. At 1004, the apparatusoutputs the first frame for transmission to the one or more wirelessnodes. FIG. 10A illustrates example components (1002A and 1004A) capableof performing the operations shown in FIG. 10 .

In some aspects, the operations 1000 may further include obtaining (bythe apparatus) a second frame (e.g., “intent to participate” frame) fromeach of at least some of the one or more wireless nodes indicating anintent to use one or more of the unused resources. The apparatus maydetermine a group of the one or more wireless nodes to participate indistributed communications with the apparatus based in part on theindication, in each second frame, of the intent to use one or more ofthe unused resources, and participate in distributed communications withthe group of wireless nodes.

FIG. 11 a flow diagram of example operations 1100 for wirelesscommunications by an apparatus, in accordance with aspects of thepresent disclosure. The operations may be performed by an apparatus suchas a slave access point (e.g., AP 110), or STA acting as an AP.

Operations 1100 begin, at 1102, where the apparatus obtains a firstframe including an indication of unused resources in a first BSSavailable to be shared with the apparatus, wherein the apparatus is in asecond BSS. The unused resources may include at least one of unusedspatial dimensions available at another apparatus in the first BSS orunused portions of spectrum in the first BSS. In some aspects, theapparatus may obtain the first frame from the other apparatus (e.g., amaster AP) in the first BSS. In some aspects, the apparatus may obtainthe first frame from an apparatus that is not located in a BSS, such asa device acting as a central processing unit, scheduler, or coordinator.At 1104, the apparatus generates a second frame including an indicationof an intent to use one or more of the unused resources. In someaspects, the second frame may further include an indication of at leastone of a number of spatial dimensions available at the apparatus or anumber of devices served by the apparatus. At 1106, the apparatusoutputs the second frame for transmission. FIG. 11A illustrates examplecomponents (1102A, 1104A and 1106A) capable of performing the operationsshown in FIG. 11 .

In some aspects, operations 1100 may further include generating (by theapparatus) one or more data frames for participating in distributedcommunications with at least another apparatus in the first BSS, afterthe second frame is output for transmission, and outputting (by theapparatus) at least one of the data frames using one or more of theunused resources. In some aspects, the apparatus may obtain one or moredata frames on the unused resources from one or more devices (e.g., STAsserved by the apparatus) in the second BSS. In some aspects, theapparatus may obtain a third (allocation) frame after the second frameis output for transmission that allocates at least one of the unusedspatial dimensions or the unused portions of spectrum, and mayparticipate in the distributed communications with the other apparatusbased on the allocated unused spatial dimensions or unused portions ofspectrum.

FIG. 12 illustrates an example scenario 1200 of frequency and spatialstream sharing across multiple BSSs, in accordance with certain aspectsof the present disclosure. Particularly, FIG. 12 shows three BSSs (BSS1,BSS2, BSS3) sharing frequency/spatial stream resources with unusedresources in BSS2 and BSS3. BSS1 includes STAs 1-4, BSS2 includes STAs5-6, and BSS3 includes STAs 7-8. In BSS1, STA 1 is allocated a 10 MHzportion 1210 of spectrum, STAs 2 and 3 are allocated a 10 MHz portion1212 of spectrum, and STAs 1 and 4 are allocated a 20 MHz portion 1214of spectrum. In BSS2, STAs 5 and 6 are allocated a 20 MHz portion 1220of spectrum, and another 20 MHz portion 1222 of spectrum is unused. InBSS3, 10 MHz portions 1232, 1234, and 1236 of spectrum are unused, andSTAs 7 and 8 are allocated a 10 MHz portion 1238 of spectrum. Note,however, that the scenario depicted in FIG. 12 is provided merely as areference example of frequency and spatial stream sharing acrossmultiple BSSs. In general, those of ordinary skill in the art willrecognize from the aspects presented herein that any number of variousdifferent frequency/spatial stream resources can be shared across BSSs.

As shown, STA 1 (from BSS1) and STAs 5, 6 (from BSS2) may be multiplexedusing a form of distributed communications (e.g., MU-MIMO) inoverlapping frequencies. For example, in the case of downlink, STAs 1,5, and 6 may be multiplexed using DL coordinated beamforming and, in thecase of uplink, STAs 1, 5, and 6 may be multiplexed using coordinated ULMU-MIMO. In addition, STAs 2 and 3 (from BSS1) and STAs 5 and 6 (fromBSS2) may be multiplexed using a form of distributed communications(e.g., DL/UL MU-MIMO) in overlapping frequencies. Similarly, STAs 1 and4 (from BSS1) and STAs 7 and 8 (from BSS3) may be multiplexed using aform of distributed communications (e.g., DL/UL MU-MIMO) in overlappingfrequencies. The portions of spectrum labeled “not used” are unusedportions of spectrum. For example, BSS2 has a single 20 MHz unusedportion 1222 of 40 MHz spectrum and BSS3 has three 10 MHz unusedportions 1232, 1234, and 1236 of 40 MHz spectrum.

Additionally or alternatively, there may be one or more unused spatialdimensions available at the APs/STAs in each BSS. In some cases, thenumber of unused spatial dimensions available at each device (e.g.,AP/STA) can be different in different portions of the spectrum in eachBSS. As a reference example, a master AP in BSS1 may have a first numberof unused spatial dimensions in the 10 MHz portion 1210 used by STA 1and a different second number of unused spatial dimensions in the 10 MHzportion 1212 used by STAs 2 and 3.

Each AP serving a group of STAs in a BSS may allocate each STA a portionof spectrum to use for distributed communications. In some cases, a STAmay be allocated one or more resource units (e.g., different portions ofspectrum and/or spatial streams) within the same BSS. As a referenceexample, FIG. 12 shows STA 1 being allocated a 10 MHz portion 1210 of 40MHz spectrum in BSS1 and being multiplexed with STA 4 in a 20 MHzportion 1214 of 40 MHz spectrum in BSS1. In some cases, a given user maybe able to participate in a distributed MU-MIMO transmission with a setof OBSS users in one part of the spectrum and the same given user may beable to participate in a distributed MU-MIMO transmission with adifferent set of OBSS users in another part of the spectrum. As areference example, FIG. 12 shows STAs 5 and 6 in BSS2 being paired withSTA 1 (from BSS1) in one 10 MHz portion 1210 of 40 MHz spectrum andbeing paired with STAs 2 and 3 (from BSS1) in another 10 MHz portion1212 of 40 MHz spectrum.

In some cases, a master-slave AP operation may be used to enabledistributed communications with unused resources shared across multipleBSSs. For example, the master AP (e.g., the BSS that startstransmission) before a given transmission (e.g., first transmission) maydetermine that it does not need the entire spectrum and/or that it hasempty spatial dimensions in certain portions of the spectrum. Referringto FIG. 9 as a reference example, the AP serving STAs 1, 2, and 3 may bethe master AP and the AP serving STAs 4, 5, and 6 may be a slave AP.Once the master AP identifies unused resources in a BSS, the master APmay invite other BSSs to participate in the distributed communicationsand perform distributed MU communications with one or more of thedevices (e.g., APs/STAs) in the other BSSs. The distributed MUcommunications may include, for example, simultaneous transmissions fromeach BSS to STAs in the BSS or simultaneous receptions from STAs in eachBSS at the BSS.

In some cases, the master AP may perform group formation, soundingand/or synchronization before a distributed communication occurs. Insome aspects, the group formation, sounding and/or synchronization maybe performed as part of a WiFi protocol. In group formation, the masterAP may prepare to transmit and determine a lack of efficient usage offrequency and spatial stream resources. For example, the master AP maydetect one or more unused resources in a BSS. The master AP may thensend out an invitation to neighboring BSSs (which may involveprioritizing certain APs) to participate in the distributed transmissionwith at least a portion of the unused resources. Note, however, thatgroup formation may happen as part of other steps (e.g., sounding,synchronization, etc.).

In the sounding and synchronization phase, the master AP may send outsynchronization frames (e.g., if slave AP(s) are not alreadysynchronized). For example, in some aspects, the apparatus (as part ofoperations 1000) may generate one or more synchronization frames forsynchronizing with the group of wireless nodes for the distributedcommunications, and output the synchronization frames for transmissionto the group of wireless nodes. The master and slave APs may alsocollect feedback, if needed, using explicit feedback mechanisms (e.g.,FIGS. 6A-6C, 7A-7C) or implicit feedback mechanisms (e.g., FIGS. 8A-8B).In some cases, however, the sounding step may not be needed (e.g., forOFDMA or UL distributed MU).

The final distributed MU transmission may be performed in variousdifferent ways. For example, the distributed MU transmission may bedistributed OFDMA only or distributed MU-MIMO only or the distributed MUtransmission may a mixture of distributed OFDMA and distributed MU-MIMO.In some cases, the distributed MU transmission may include occasionalsynch messages from the master AP.

FIG. 13 illustrates an example group formation protocol 1300 for sharingunused resources for distributed communications, in accordance withcertain aspects of the present disclosure. In this example, AP1 is themaster AP (of BSS1). AP2 (of BSS2) and AP3 (of BSS3) are slave APs.Group formation may occur via over the air messages or via a backhaul.As shown, AP1 may initiate a group formation procedure by sending aspecial trigger message (e.g., Distributed (Dist) MU group formationtrigger) to neighboring APs (AP2 and AP3).

The Dist MU group formation trigger may indicate whether there areunused resources in BSS1 available to be shared with AP2 and AP3. Forexample, the Dist MU group formation trigger may include at least one ofthe number of empty spatial dimensions available at the master AP (e.g.,in various resource units of frequency) or the frequency units (e.g.,portions of spectrum) that are unused in BSS1.

In response to the Dist MU group formation trigger, each neighboring APmay reply with an intent to use one or more of the unused resources. Forexample, each neighboring AP may send an “intent to participate” frame(e.g., Dist MU Intent to participate frame) to the master AP. As shownin FIG. 13 , for example, AP2 and AP3 both transmit an “intent toparticipate” frame indicating an intent to use one or more of the unusedresources for a distributed communication with the master AP. The“intent to participate” frame may be sent sequentially or simultaneouslyby each neighboring AP. The “intent to participate” frame may include alist of STAs served by the neighboring AP and/or potential streamallocations (e.g., a number of spatial dimensions available at theneighboring AP) in various frequency resource units. The master AP mayuse this information to determine the number of nulling dimensionsavailable at the neighboring AP. The “intent to participate” frame maybe sent using open loop MU-MIMO (e.g., similar to UL MU-MIMO) or ULOFDMA.

In some cases, based on the “intent to participate” frames, the masterAP may respond by allocating one or more of the unused resources to theneighboring APs. For example, the apparatus (as part of operations 1000)may generate, after obtaining the second (“intent to participate”)frames, a third frame allocating at least one of the unused resources tothe wireless nodes that sent the second frames. In some aspects, ifneighboring APs respond with an intent to use more streams and/orfrequency resources that can be accommodated, the master AP can dropsome APs, reduce the stream/frequency resources per AP, etc. The masterAP can update the resource allocation for each AP via an allocationframe. As shown in FIG. 13 , for example, the master AP may send an(optional) allocation frame (e.g., “Final Dist MU group config”) toallocate the unused resources among the neighboring APs.

To determine the allocation, the master AP may prioritize the requests(e.g., within the “intent to participate” frames) based on one or morecriteria. For example, the master AP may determine the allocation basedon a number of received “intent to participate” frames, interferenceconditions, re-use situations, a reciprocal agreement of prioritybetween the master AP and one or more neighboring APs, etc. In somecases, the master AP may send the allocation frame in a different phaseof the WiFi protocol. For example, the allocation frame may be combinedwith an NDPA of the sounding phase or another trigger to start thedistributed MU transmission.

In the sounding phase of FIG. 13 , the master AP may use any of theabove described communication sounding protocols (e.g., FIGS. 6A-6C,7A-7C and 8A-8B). In some aspects, however, the master AP during thesounding phase may be able to request partial band feedback (e.g.,feedback for 10 MHz of a 40 MHz spectrum, or in general, another partialband of a larger spectrum) from each STA.

For DL or UL distributed MU transmissions, synchronization among APs maybe similar to synchronization performed for inter-STAs for UL OFDMA.That is, the synchronization requirements may be no worse than thesynchronization requirements for UL OFDMA. To improve synchronization,the master AP can send a trigger before the distributed communications.

In the case of a multi-AP or multi-STA NDP, there may be one or moreimplications for tracking during LTFs for NDP. For example, in theabsence of complete synchronization across all transmitters, multiplelocal oscillators (LOs) may have to potentially be tracked. Thisscenario may be different from other cases (e.g., 11ac/11ax DL MU-MIMO)where a single LO is tracked. In some cases, tracking multiple LOs mayuse techniques similar to those in UL MU-MIMO (e.g., in flax) wheremultiple STAs transmit to one AP at the same time.

In some cases, if different APs are FDM′d in frequency, phase trackingper transmitter may become easier (e.g., just have pilots for differentAPs on non-overlapping tones). If different transmitters are TDM′d intime, phase tracking per transmitter may still be possible. However, itmay be beneficial to interleave the symbols of one transmitter ratherthan have consecutive symbols belonging to one AP. If a P-matrix isused, then there may be multiple options for tracking. In one option,multi-stream pilots can be used. In another option, non-overlappingpilot tones can be given to different transmitters. In the case ofmulti-stream pilots, there may be one stream per AP on pilot tones orthe number of streams per AP on pilot tones may be equal to the numberof streams given to that transmitter in the LTF section.

There may also be multiple options for pilots during data. In a firstoption, there may be one stream per transmitter on the pilot tones. In asecond option, the number of streams per transmitter on pilot tones maybe same as the data tones allocated to it. In a third option,non-overlapping pilot tones may be given to different transmitters. Forexample, there may be one stream for each transmitter on the allocatedpilot tones or a same number of streams for each transmitter as its datatones.

The methods disclosed herein comprise one or more steps or actions forachieving the described method. The method steps and/or actions may beinterchanged with one another without departing from the scope of theclaims. In other words, unless a specific order of steps or actions isspecified, the order and/or use of specific steps and/or actions may bemodified without departing from the scope of the claims.

As used herein, a phrase referring to “at least one of” a list of itemsrefers to any combination of those items, including single members. Asan example, “at least one of: a, b, or c” is intended to cover a, b, c,a-b, a-c, b-c, and a-b-c, as well as any combination with multiples ofthe same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b,b-b-b, b-b-c, c-c, and c-c-c or any other ordering of a, b, and c). Asused herein, including in the claims, the term “and/or,” when used in alist of two or more items, means that any one of the listed items can beemployed by itself, or any combination of two or more of the listeditems can be employed. For example, if a composition is described ascontaining components A, B, and/or C, the composition can contain Aalone; B alone; C alone; A and B in combination; A and C in combination;B and C in combination; or A, B, and C in combination.

As used herein, the term “determining” encompasses a wide variety ofactions. For example, “determining” may include calculating, computing,processing, deriving, investigating, looking up (e.g., looking up in atable, a database or another data structure), ascertaining and the like.Also, “determining” may include receiving (e.g., receiving information),accessing (e.g., accessing data in a memory) and the like. Also,“determining” may include resolving, selecting, choosing, establishingand the like.

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the claims are not intended to be limited to theaspects shown herein, but is to be accorded the full scope consistentwith the language claims, wherein reference to an element in thesingular is not intended to mean “one and only one” unless specificallyso stated, but rather “one or more.” For example, the articles “a” and“an” as used in this application and the appended claims shouldgenerally be construed to mean “one or more” unless specified otherwiseor clear from the context to be directed to a singular form. Unlessspecifically stated otherwise, the term “some” refers to one or more.Moreover, the term “or” is intended to mean an inclusive “or” ratherthan an exclusive “or.” That is, unless specified otherwise, or clearfrom the context, the phrase, for example, “X employs A or B” isintended to mean any of the natural inclusive permutations. That is, forexample the phrase “X employs A or B” is satisfied by any of thefollowing instances: X employs A; X employs B; or X employs both A andB. All structural and functional equivalents to the elements of thevarious aspects described throughout this disclosure that are known orlater come to be known to those of ordinary skill in the art areexpressly incorporated herein by reference and are intended to beencompassed by the claims. Moreover, nothing disclosed herein isintended to be dedicated to the public regardless of whether suchdisclosure is explicitly recited in the claims. No claim element is tobe construed under the provisions of 35 U.S.C. § 112, sixth paragraph,unless the element is expressly recited using the phrase “means for” or,in the case of a method claim, the element is recited using the phrase“step for.”

The various operations of methods described above may be performed byany suitable means capable of performing the corresponding functions.The means may include various hardware and/or software component(s)and/or module(s), including, but not limited to a circuit, anapplication specific integrated circuit (ASIC), or processor. Generally,where there are operations illustrated in figures, those operations mayhave corresponding counterpart means-plus-function components withsimilar numbering. For example, operations 1000 and 1100 illustrated inFIGS. 10 and 11 correspond to means 1000A and 1100A illustrated in FIGS.10A and 11A, respectively.

For example, means for transmitting, means for sending, and/or means forindicating may comprise a transmitter (e.g., the transmitter unit 222)and/or an antenna(s) 224 of the access point 110, a transmitter (e.g.,the transmitter unit 254) and/or antenna(s) 252 of the user terminal 120illustrated in FIG. 2 , or the (transmitter 310 of) transceiver 314 ofthe wireless device 302 illustrated in FIG. 3 . Means for receiving maycomprise a receiver (e.g., the receiver unit 222) and/or an antenna(s)224 of the access point 110, a receiver (e.g., the receiver unit 254)and/or antenna(s) 252 of the user terminal 120 illustrated in FIG. 2 ,or the (receiver 312 of) transceiver 314 of the wireless device 302illustrated in FIG. 3 .

Means for processing, means for generating, means for sharing, means forselecting, means for performing, means for decoding, means for using,means for participating, means for synchronizing, means for indicating,means for deciding, means for allocating, and/or means for determining,may comprise a processing system, which may include one or moreprocessors, such as the RX data processor 242, the TX data processor210, the TX spatial processor 220, and/or the controller 230 of theaccess point 110 or the RX data processor 270, the TX data processor288, the TX spatial processor 290, and/or the controller 280 of the userterminal 120 illustrated in FIG. 2 , or the processor 304 of thewireless device 302 illustrated in FIG. 3 .

In some cases, rather than actually transmitting a frame a device mayhave an interface to output a frame for transmission (a means foroutputting). For example, a processor may output a frame, via a businterface, to a radio frequency (RF) front end for transmission.Similarly, rather than actually receiving a frame, a device may have aninterface to obtain a frame received from another device (a means forobtaining). For example, a processor may obtain (or receive) a frame,via a bus interface, from an RF front end for reception.

The various illustrative logical blocks, modules and circuits describedin connection with the present disclosure may be implemented orperformed with a general purpose processor, a digital signal processor(DSP), an application specific integrated circuit (ASIC), a fieldprogrammable gate array (FPGA) or other programmable logic device (PLD),discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general-purpose processor may be a microprocessor, but in thealternative, the processor may be any commercially available processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

If implemented in hardware, an example hardware configuration maycomprise a processing system in a wireless node. The processing systemmay be implemented with a bus architecture. The bus may include anynumber of interconnecting buses and bridges depending on the specificapplication of the processing system and the overall design constraints.The bus may link together various circuits including a processor,machine-readable media, and a bus interface. The bus interface may beused to connect a network adapter, among other things, to the processingsystem via the bus. The network adapter may be used to implement thesignal processing functions of the PHY layer. In the case of a userterminal 120 (see FIG. 1 ), a user interface (e.g., keypad, display,mouse, joystick, etc.) may also be connected to the bus. The bus mayalso link various other circuits such as timing sources, peripherals,voltage regulators, power management circuits, and the like, which arewell known in the art, and therefore, will not be described any further.The processor may be implemented with one or more general-purpose and/orspecial-purpose processors. Examples include microprocessors,microcontrollers, DSP processors, and other circuitry that can executesoftware. Those skilled in the art will recognize how best to implementthe described functionality for the processing system depending on theparticular application and the overall design constraints imposed on theoverall system.

If implemented in software, the functions may be stored or transmittedover as one or more instructions or code on a computer readable medium.Software shall be construed broadly to mean instructions, data, or anycombination thereof, whether referred to as software, firmware,middleware, microcode, hardware description language, or otherwise.Computer-readable media include both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. The processor may beresponsible for managing the bus and general processing, including theexecution of software modules stored on the machine-readable storagemedia. A computer-readable storage medium may be coupled to a processorsuch that the processor can read information from, and write informationto, the storage medium. In the alternative, the storage medium may beintegral to the processor. By way of example, the machine-readable mediamay include a transmission line, a carrier wave modulated by data,and/or a computer readable storage medium with instructions storedthereon separate from the wireless node, all of which may be accessed bythe processor through the bus interface. Alternatively, or in addition,the machine-readable media, or any portion thereof, may be integratedinto the processor, such as the case may be with cache and/or generalregister files. Examples of machine-readable storage media may include,by way of example, RAM (Random Access Memory), flash memory, phasechange memory, ROM (Read Only Memory), PROM (Programmable Read-OnlyMemory), EPROM (Erasable Programmable Read-Only Memory), EEPROM(Electrically Erasable Programmable Read-Only Memory), registers,magnetic disks, optical disks, hard drives, or any other suitablestorage medium, or any combination thereof. The machine-readable mediamay be embodied in a computer-program product.

A software module may comprise a single instruction, or manyinstructions, and may be distributed over several different codesegments, among different programs, and across multiple storage media.The computer-readable media may comprise a number of software modules.The software modules include instructions that, when executed by anapparatus such as a processor, cause the processing system to performvarious functions. The software modules may include a transmissionmodule and a receiving module. Each software module may reside in asingle storage device or be distributed across multiple storage devices.By way of example, a software module may be loaded into RAM from a harddrive when a triggering event occurs. During execution of the softwaremodule, the processor may load some of the instructions into cache toincrease access speed. One or more cache lines may then be loaded into ageneral register file for execution by the processor. When referring tothe functionality of a software module below, it will be understood thatsuch functionality is implemented by the processor when executinginstructions from that software module.

Also, any connection is properly termed a computer-readable medium. Forexample, if the software is transmitted from a website, server, or otherremote source using a coaxial cable, fiber optic cable, twisted pair,digital subscriber line (DSL), or wireless technologies such as infrared(IR), radio, and microwave, then the coaxial cable, fiber optic cable,twisted pair, DSL, or wireless technologies such as infrared, radio, andmicrowave are included in the definition of medium. Disk and disc, asused herein, include compact disc (CD), laser disc, optical disc,digital versatile disc (DVD), floppy disk, and Blu-ray® disc where disksusually reproduce data magnetically, while discs reproduce dataoptically with lasers. Thus, in some aspects computer-readable media maycomprise non-transitory computer-readable media (e.g., tangible media).In addition, for other aspects computer-readable media may comprisetransitory computer-readable media (e.g., a signal). Combinations of theabove should also be included within the scope of computer-readablemedia.

Thus, certain aspects may comprise a computer program product forperforming the operations presented herein. For example, such a computerprogram product may comprise a computer-readable medium havinginstructions stored (and/or encoded) thereon, the instructions beingexecutable by one or more processors to perform the operations describedherein. For example, instructions for performing the operationsdescribed herein and illustrated in the appended figures.

Further, it should be appreciated that modules and/or other appropriatemeans for performing the methods and techniques described herein can bedownloaded and/or otherwise obtained by a user terminal and/or basestation as applicable. For example, such a device can be coupled to aserver to facilitate the transfer of means for performing the methodsdescribed herein. Alternatively, various methods described herein can beprovided via storage means (e.g., RAM, ROM, a physical storage mediumsuch as a compact disc (CD) or floppy disk, etc.), such that a userterminal and/or base station can obtain the various methods uponcoupling or providing the storage means to the device. Moreover, anyother suitable technique for providing the methods and techniquesdescribed herein to a device can be utilized.

It is to be understood that the claims are not limited to the preciseconfiguration and components illustrated above. Various modifications,changes and variations may be made in the arrangement, operation anddetails of the methods and apparatus described above without departingfrom the scope of the claims.

What is claimed is:
 1. A method for wireless communication performed byan apparatus, the method comprising: identifying a set of unusedresources in a first basic service set (BSS); determining a group of oneor more wireless nodes in a second BSS to participate in distributedcommunications with the apparatus; allocating at least a portion of theset of unused resources to the group of the one or more wireless nodes;and participating in distributed communications with the group of theone or more wireless nodes with at least the portion of the set ofunused resources.
 2. The method of claim 1, further comprisingparticipating in a group formation procedure with the one or morewireless nodes in the second BSS.
 3. The method of claim 2, wherein thegroup of the one or more wireless nodes is determined based on the groupformation procedure.
 4. The method of claim 2, wherein the group of theone or more wireless nodes comprises a subset of a plurality of wirelessnodes in the second BSS.
 5. The method of claim 2, wherein participatingin the group formation procedure comprises initiating the groupformation procedure with the one or more wireless nodes.
 6. The methodof claim 5, wherein initiating the group formation procedure comprisestransmitting to the one or more wireless nodes a message including anindication of the set of unused resources in the first BSS.
 7. Themethod of claim 1, wherein the set of unused resources comprise unusedspatial dimensions available at the apparatus.
 8. The method of claim 7,wherein the unused spatial dimensions available at the apparatuscomprise: a first number of the unused spatial dimensions available atthe apparatus in a first portion of spectrum in the first BSS; and asecond number of the unused spatial dimensions available at theapparatus in a second portion of spectrum in the first BSS.
 9. Themethod of claim 1, wherein the set of unused resources comprise unusedportions of spectrum in the first BSS.
 10. An apparatus comprising: atleast one processor configured to: identify a set of unused resources ina first basic service set (BSS); determine a group of one or morewireless nodes in a second BSS to participate in distributedcommunications with the apparatus; allocate at least a portion of theset of unused resources to the group of the one or more wireless nodes;and participate in distributed communications with the group of the oneor more wireless nodes with at least the portion of the set of unusedresources; and a memory coupled to the at least one processor.
 11. Theapparatus of claim 10, wherein the at least one processor is furtherconfigured to participate in a group formation procedure with the one ormore wireless nodes in the second BSS.
 12. The apparatus of claim 11,wherein the group of the one or more wireless nodes is determined basedon the group formation procedure.
 13. The apparatus of claim 11, whereinthe group of the one or more wireless nodes comprises a subset of aplurality of wireless nodes in the second BSS.
 14. The apparatus ofclaim 11, wherein the at least one processor is configured toparticipate in the group formation procedure by initiating the groupformation procedure with the one or more wireless nodes.
 15. Theapparatus of claim 14, wherein the at least one processor is configuredto initiate the group formation procedure by generating a messageincluding an indication of the set of unused resources in the first BSS,the apparatus further comprising a transmitter configured to transmitthe message to the one or more wireless nodes.
 16. The apparatus ofclaim 10, wherein the set of unused resources comprise unused spatialdimensions available at the apparatus.
 17. The apparatus of claim 16,wherein the unused spatial dimensions available at the apparatuscomprise: a first number of the unused spatial dimensions available atthe apparatus in a first portion of spectrum in the first BSS; and asecond number of the unused spatial dimensions available at theapparatus in a second portion of spectrum in the first BSS.
 18. Theapparatus of claim 10, wherein the set of unused resources compriseunused portions of spectrum in the first BSS.
 19. A non-transitorycomputer-readable medium comprising processor-executable instructions tocause one or more processors to: identify a set of unused resources in afirst basic service set (BSS); determine a group of one or more wirelessnodes in a second BSS to participate in distributed communications;allocate at least a portion of the set of unused resources to the groupof the one or more wireless nodes; and participate in distributedcommunications with the group of the one or more wireless nodes with atleast the portion of the set of unused resources.
 20. The non-transitorycomputer-readable medium of claim 19, wherein the one or more processorsare further configured to participate in a group formation procedurewith the one or more wireless nodes in the second BSS.
 21. Thenon-transitory computer-readable medium of claim 20, wherein the one ormore processors are configured to participate in the group formationprocedure by initiating the group formation procedure with the one ormore wireless nodes.
 22. The non-transitory computer-readable medium ofclaim 19, wherein the set of unused resources comprise unused spatialdimensions available at the apparatus.
 23. The non-transitorycomputer-readable medium of claim 19, wherein the set of unusedresources comprise unused portions of spectrum in the first BSS.
 24. Anapparatus for wireless communications, comprising: means for identifyinga set of unused resources in a first basic service set (BSS); means fordetermining a group of one or more wireless nodes in a second BSS toparticipate in distributed communications with the apparatus; means forallocating at least a portion of the set of unused resources to thegroup of the one or more wireless nodes; and means for participating indistributed communications with the group of the one or more wirelessnodes with at least the portion of the set of unused resources.
 25. Theapparatus of claim 24, further comprising: means for participating in agroup formation procedure with the one or more wireless nodes in thesecond BSS.
 26. The apparatus of claim 25, further comprising: means forinitiating the group formation procedure with the one or more wirelessnodes.
 27. The apparatus of claim 26, further comprising: means forgenerating a message including an indication of the set of unusedresources in the first BSS.
 28. The apparatus of claim 24, wherein theset of unused resources comprise unused spatial dimensions available atthe apparatus.
 29. The apparatus of claim 24, wherein the set of unusedresources comprise unused portions of spectrum in the first BSS.